1. Field of the Invention
This disclosure relates to determining an voltage of an AC main at a device that does not directly receive the AC mains voltage mains signal and does not receive the complete sinusoidal AC mains signal.
2. Description of the Related Art
Switching power supplies are used to provide efficient, regulated power to electronic devices. Power supplies that are coupled to the alternating current (AC) mains are commonly referred to as “offline power supplies.” Worldwide, there are two predominate AC mains operating ranges; (a) 120 AC voltage (VAC) has a range of approximately 85 VAC to 135 VAC (referred to herein when describing some embodiments as the LOW-range), and (b) 220 VAC has a range of approximately 170 VAC to 270 VAC (referred to herein when describing some embodiments as the HIGH-range). Universal power supplies, commonly referred to offline power supplies, can be connected to either AC mains voltage ranges, allowing electronic device manufacturers the convenience of designing a single product suitable for worldwide distribution. Many universal power supplies detect the AC mains operating range, e.g., LOW-range or HIGH range, in order to make operational adjustments such as modulation parameters, protection thresholds, over-voltage protection (OVP) and under-voltage protection (UVP), for example.
In conventional environments, there is a direct connection of the offline power supply to the AC mains, the voltage range can be determined simply using peak detection or V-RMS sensing. However, in the case of devices such as LED-based bulbs, the bulb may be either coupled directly to the AC mains, or indirectly through a phase cut dimmer switch. In the case where it is an indirect connection via a phase cut dimmer switch, the AC mains voltage range cannot be determined using peak detection or V-RMS sensing. Therefore, prior art bulbs are unable to optimize control and other operations due to the inability to determine the AC mains operating range.